This invention relates to a method for the purification of hydrogen peroxide and, more particularly, to a method which is capable of producing hydrogen peroxide of the highest quality, that is suitable for use in the electronics industry as a cleaning agent.
Perhaps the most single problem being experienced in the electronics industry at the present time is the effect of contamination during the manufacture of microcircuit devices, such as chips and wafers. As these devices become more complex, and smaller in dimension, sensitivity to the presence of contaminants becomes more of a problem and to the extent wherein acceptable quality of product cannot be achieved, such contaminants, in the form of solid particles, can open or short circuit, affect photolithographic reproduction, alter electrical properties and even damage the crystal structure of these electronic devices.
One of the obvious steps which has been pursued in order to eliminate, or at least to reduce the effects of contamination to an acceptable limit, is in the improvements relating to the cleansing of electronic devices themselves and to the cleansing media used in such cleaning steps. In some instances, very elaborate steps must be taken to clean or purify one or more of the ingredient agents utilized in the cleaning medium used in removing contaminants from an electronic device, say, for example, in a wafer cleaning process.
The presence of contaminant ions in chemicals supplied to the electronics industry is currently a major concern as users insist on ultrapure reagents for their processes. The Semi-Conductor Equipment and Materials Institute has established standards which greatly reduced the parts-per-billion level, and further reductions are always in prospect.
Despite even the most well documented cleaning processes, contamination still occurs. As known in the art, wafer cleaning processes include liquid and gas-phase chemical techniques as well as physical means such as scrubbing, pressurized fluid jets, ultrasonics and megasonics. Of the many cleaning methods which have been tested and evaluated, the most effective procedures have utilized hydrogen peroxide as a cleaning agent. While hydrogen peroxide is presently considered as the most effective cleaning agent for cleaning wafers and the like, present day production of this agent has not been able to provide the electronics industry with such agents with sufficient purity that will enable the industry, in turn, to produce high quality products.
Hydrogen peroxide use in the electronics industry is expected to grow by 10-20% annually. The current products are expected to be unacceptable for the needs of the semi-conductor manufacturers in the years ahead. Conventional methods for purifying hydrogen peroxide has included the treatment of the reagent with various grades of carbon combined with washing steps of different temperatures and times. However, these pretreatments of reagents, in themselves, were the cause of the increase of contaminants in the final peroxide product.
In the East German Patent DD 216,701, dated Dec. 19, 1984, a specific method is disclosed for purifying hydrofluoric acid using activated carbon treated with ammonium carbonate.